[COURSE] "La biblia de Node.js".

Section 05 - Refreshing JS (ES6)

Basics - from callback to promises.

-> Callback

A function who serves as argument to another function, the second one can call it.

Advantages	Disadvantages
Simple, conceptually	Rough, when nesting many (Callback hell)
Universal, they are JS native	Little intuitive, to understand the flow is tedious

Notes

· First callback argument allways will be the error.

-> Promise

Object which represent the end or fail of a asinconous operation.

Advantages	Disadvantages
Easily chaining, clair and easy to chain hadling a flow	No exceptions, require .catch() method to handel errors
Powerfull, really capable to handle complex async ops

Notes

· use promise instead callbacks. Watch out with promise hell.

-> async/await

An async function returns a Promise object. If the function return a value the promise resolve that value and if throws an error or falls on a exception it reject that error or exception.

The await stops an async execution until a promise will resolve or reject. |

Notes

· requires a tryCatch block.

Section 07 - Sync vs async

Libuv, Event loop and Non-blocking IO

Libuv it's a C++ library to manage OS events. It's who 'talks' to the OS.
Works togheter with V8.

Libuv has a queue of finished events (Systems events). For each loop Libuv checs that queue, if are something perform a callback to V8.

Non-blocking IO: Capability to make actions without stop others.

Note: V8, Libuv and Javascript are all sincronous.
NodeJS performs actions asynchronous (if we tell to do it)

Section 08 - HTTP and web servers.

-> HTTP

Protocol over which communicate the client and server.

-> Web server

Software which delivers contents requered by the client. It's distinct to a server (hardware).

-> NodeJS and web server.

Some details:

• Node can create it's own web server. Includes the tools for it.
• Low fault tolerance. An unhandled error can down a server.
• Frameworks vs vanilla. Both ways can be taken to mount a webserver.

Client server basic comunication.

The client sends a request to the server, the server process it and return a response. Both, client and server, knows information about each other (like OS, browser, ports and so on) by the request and response.

HTTP methods

METHOD	Standard use
GET	Read a resource
POST	Create a new resource
PUT	Update an existing resource
PATCH	Update a property of an existing resource
DELETE	Remove an existing resource

Middleware

A middleware it's code that run between the start of therequest and the endpoint of the server.

MVC

Model View Controller Code design pattern who sepair the code about responsibilities.

Section 09 - Databases.

SQL databases starts using at 80s. NoSQL databases are newer.

SQL	NoSQL
Organize the information on chunks relating between them through unique Id	Extremely usefull when we need to store very changing data
Group the info in "tables"	Group the info in "collections"
Meets ACID props (make the system strong and less vulnerable)
Engines: MSSQL, Oracle, Postgres, MySQL, SQLite, and more	Engines: MongoDB, Cassandra, RethinkDB, FirebaseDB, Redis, and more

ORM

Object Relational Mapping it's a software model which map db tables on entities for a easily handling.

ODM

Object Document Mapping, same as ORM but document oriented.

NodeJS - process.argv

It's the process property which store the command line arguments passed to node when the command runs.
By default argv stores:

0. node path.
1. file which node runs path.
2. and more, the rest of params.

Section 10 - Frontend and backend.

Frontend

Visual interface which can user interact with a software or process.

Backend

Piece of software that handle business logic and data persistence.

Frameworks

Piece of software that works as base and organization on a software development. Frameworks examples

• Frontend: Angular, React, Vue, Svelte, Ember.
• Backend: NextJS, sails, express, adonis.

When use a framework?	When NO use a framework?
Looking for community support	Have not community support
Fast developmente time	We don't know the language
Other tools transparent integration	We fall into the frameworks fashion

Typescript

Open source programming language, Microsoft leadered, with OOP tools for big projects. It's a superset of Javascript.

Note: tsc CLI for Typescript.

YES TS	NO TS
Big projects	Weak OOP knowledge
Teams with strong OOP knowledge	Type it's a problem
Constant evolving

Superset

Language writen over another.

Section 11 - APIs architecture.

APIs

An API:

• Reduce software coupling.
• Aggregate differential value to an enterprise.

It's a group of protocols and difinitions used to develop and integrate software. API stands for Application Programming Interface.

Software architecture

General and reusable solution to a common problem on software development. This group of technics anwers questions like:

• What programming language use?
• What framwork?
• Use disegne patterns?
• How handle project scafolding?
• What DB to use?
• So on

Some common architectures are:

• Client/server architecture.
• N layers architecture.
• Bus events architectures.
• Master/slave architecture.
• Anothers

N layers architecture

Commonly used for APIs and desktop apps.

Client/server architecture

Low coupling apps like mobile apps and APIs

RESTful

REST stands for REpresentational State Transfer. REST are some principles which describe how to resources are defined and accessed through a web service.\

A web server which implements REST principles is called RESTful.

Some RESTful details:

• Clean and intuitive URIs.
• Use JSON or XML format info.

The REST architecture focus on:

• Performance.
• Scalability.
• Simplicity.
• Portability.
• Reliability.

REST principles

1. Client/server

The backend and frontend (in this case for web apps) are completly separated. Two diferent frameworks.

2. Layers system

The layers are sorted hierarchically and restricted to the layers next to.

3. Stateless

A request must contain all data for the server understand and build the context to process it.

4. Uniform interface

Are guided for:

1. Resource identification.
2. Resource manipulation.
3. Self-descriptive repsonses.
4. State administration (throught HATEOAS)

These four pilars are handled throught: HTTP Verbs, Media types and HETEOAS.

5. Cache

Derived of stateless, all responses need explicitly tagged as cacheble or not cacheble.

6. Code on demand (optional).

Allow a client access to resources not knowing how to process it.

Section 12 - Docker.

Docker it's a container handler. Docker it's a container handler. The main idea it's the creation of isolateds, lightweight and portable containers in which the apps runs so getting easily deploys.

It's a tool developer and testers oriented.

Summary:

1. To create a container we need an image, DockerHUB it's a good place to start looking for.
2. An image it's created by a Dockerfile.
3. A Dockerfile it's instruction based.
4. An image could be shared and reused.
5. The container data persists ONLY on volumes.

Section 13 - Microservices.

Monolite architecture.

It's one and only autonomic programm unit.

Advantages	Disadvantages
Easy to develop	No flexible
Easy to test	Hard to maintain
Easy work alone	Hard to scale
Easy to deploy	Unreliable potential

Microservices architecture.

"Microservices are reached by pain, not pleasure"

Collection of autonomous and small services.

Features:

• One and only resposability.
• Persistence.
• Resilience.
• Logs.
• API good defined.

Advantages	Disadvantages
Easy scale	Hard e2e test
Allo technologies mixing	More chance to duplicates
Trustable potential	Information integrity
Tranparents deploy	More specialized workteams

Section 14 - CI/CD.

Continuous integration.

Process where every change to our app must be tested and verified by tests.

Some tools: TravisCI, Azure DevOps, Jenkins...

Continuous delivery.

Similar to CI but the tests must to ensure that every change are production ready. The production deploy still manual.

Continuous deployment.

Similar to continuous delivery but runs until production.

Pipeline.

Steps to follow on a devops process.

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#NodeJS
#JavaScript
#ES6
#express.js
#HTTP
#SQL
#NoSQL
#sequelize
#mongoose
#backend
#frontend